The present invention belongs to the technical field of a finely-divided powder spray apparatus for discharging finely-divided powder together with a gas stream from an inclined spray nozzle pipe and spraying the finely-divided powder onto a member to be sprayed such as a substrate and the like.
There is known a liquid crystal spacer spray apparatus as a representative example of the finely-divided powder spray apparatus, the apparatus uniformly spraying liquid crystal spacers (spacer beads) as finely-divided powder having a uniform particle size between liquid crystal substrates constituting a liquid crystal display panel used to a liquid crystal display device and the like, for example, between a glass sheet and a glass sheet or a plastic substrate in a prescribed amount so that the liquid crystal spacers are formed to a single layer.
In the liquid crystal display panel of the liquid crystal display device and the like, particles (spacer beads) having a uniform particle size of about several microns to several tens of microns are sprayed or coated as spacers as uniformly as possible in an amount of 10 to 2000 particles in a unit area of 1 mm.sup.2 in order to form a space into which liquid crystal is charged between a glass sheet serving as a liquid crystal substrate and a glass sheet or a plastic (organic glass, etc.) substrate other than the glass sheet or between a plastic substrate and a glass substrate (hereinafter, the glass substrate will be described as a representative example and the above members are referred to as glass substrates as a whole). Various types of plastic particles and silica particles are used as the liquid crystal spacers.
There have been known liquid crystal spacer spray apparatuses as an apparatus for uniformly spraying a prescribed amount of the liquid crystal spacers onto the glass sheet serving as the liquid crystal substrate in a single layer.
As the liquid crystal spacer spray apparatus, there have been used spray apparatuses for uniformly spraying the liquid crystal spacers onto the glass substrate by suspending the liquid crystal spacers in a liquid of chlorofluorocarbon, etc. in a colloid state, uniformly spraying the spacers onto the glass sheet in a liquid state and vaporizing the liquid of chlorofluorocarbon, etc. However, these spray apparatuses using chlorofluorocarbon, etc. cannot be used because the use of chlorofluorocarbon, etc is restricted or prohibited due to the problem of environmental pollution.
To cope with the above circumstances, there have been proposed liquid crystal spacer spray apparatuses using a gas such as air, a nitrogen gas, etc. in place of chlorofluorocarbon. These liquid crystal spacer spray apparatuses transport fine liquid crystal spacer particles (spacer beards) together with a gas flow of the air, the nitrogen gas, etc. through a thin pipe (transportation pipe) and discharge the particles form a swinging spray nozzle pipe together with the gas flow so that they are sprayed onto the glass substrate.
However, since the liquid crystal spacer particles are composed of finely-divided powder having a particle size of several microns to several tens of microns, they are liable to float. Further, since the liquid crystal spacer particles are composed of various types of plastic particles or silica particles, they are liable to be charged and it is difficult to spray them onto the glass substrate at a prescribed density with excellent reproducibility. Therefore, the liquid crystal spacer particles are charged in accordance with a charged polarity (electrostatic polarity) as well as the glass substrate and a table are grounded to permit the liquid crystal spacer particles to be reliably sprayed onto the glass substrate in the prescribed density.
In the liquid crystal spacer spray apparatus, the spray nozzle pipe which performs a swing motion to discharge the liquid crystal spacer particles together with the gas flow is conventionally arranged such that it is swung in an X-axis direction and a Y-axis direction, respectively by a crank or an eccentric cam coupled with a motor and the inclinations of the spray nozzle pipe in the X-axis direction and the Y-axis direction are combined so that the spray nozzle pipe sprays the liquid crystal spacer particles onto the glass substrate as shown in FIG. 8A.
In the conventional liquid crystal spacer spray apparatus, the spray nozzle pipe reciprocates once in the Y-axis direction while it reciprocates a plurality of times (6 times in the illustrated example) in the X-axis direction as apparent from FIG. 8A which shows an example of the center locus of a path along which the liquid crystal spacers are to be sprayed onto the glass substrate.
The spray nozzle pipe is swung in such an arrangement that it is supported by a spherical bearing at the center thereof and driven by a crank or an eccentric cam at the upper portion thereof.
Recently, since the size of a liquid crystal display panel is increased gradually as well as a plurality of liquid crystal display panels are often made from a single glass substrate, it is required to spray the liquid crystal spacers to a wider area. To cope with the requirement, there is a tendency that a swing angle required to the spray nozzle pipe for spraying the liquid crystal spacers is increased.
To spray the liquid crystal spacers onto a large glass substrate, it is necessary to increase the size of the table on which the glass substrate is mounted and the height of a chamber, or to increase the swing angle of the spray nozzle pipe. When, however, the swing angle of the spray nozzle pipe of the conventional liquid crystal spacer spray apparatus is increased, the swing speed of the spray nozzle pipe is limited by the speed thereof in the X-axis direction because the spray nozzle pipe is swung at a very high speed in the X-axis direction as compared with the swing speed thereof in the Y-axis direction as well as the durability of the spray nozzle pipe in the X-axis direction is apparently different from the durability thereof in the Y-axis direction.
Whereas, when the size of the table of the glass substrate and the height of the chamber are increased to spray the liquid crystal spacers onto the large glass substrate, the size of the spray apparatus itself can be also increased. However, since the height of the ceiling of a clean room in which the liquid crystal spacers are sprayed is limited, the clean room must be specially designed to increase the height of the ceiling thereof. Thus, there is arisen a problem that the cost of the clean room is increased. In particular, when the size of the glass substrate is further increased hereinafter and a glass substrate of about 1000 mm.times.1000 mm is made, there is problem that a conventional spray system cannot be accommodated in a currently used clean room.
Since the spray nozzle pipe is swung by the crank or the eccentric cam, the spray nozzle pipe does not move at a constant speed and the moving speed of it greatly varies at both the ends thereof. Therefore, the spray nozzle pipe must spray the liquid crystal spacers to an area which is sufficiently larger than a glass substrate 16, by which a useless space is required to the periphery of the glass substrate as shown in FIG. 8.
Further, since the spray nozzle pipe is swung by the crank or the eccentric cam, the center of the locus of a spray path along which the liquid crystal spacers are sprayed onto the glass substrate is located on a prescribed moving path and moves at a prescribed moving speed. Accordingly, since it is difficult to partly change the moving path and the moving speed, even if the liquid crystal spacers are partly irregularly sprayed, the spray of them cannot be corrected.